Effects of peripheral administration of naloxone on beta-adrenergic mediated responses.
A possible interaction between the opiate and beta-adrenergic systems in controlling body temperature, heart rate and water intake was investigated using adult male Sprague-Dawley rats. Peripheral administration of isoproterenol (8 and 50 micrograms/kg, s.c.) produced significant elevations of heart rate and tail skin and colonic temperatures, respectively. Peripheral pretreatment with naloxone (1 mg/kg, s.c.) was without effect on these beta-adrenergic responses. Administration of isoproterenol (25 micrograms/kg, s.c.) produced a significant increase in water intake which was abolished by peripheral pretreatment with naloxone (1 mg/kg, s.c.). Previous studies have suggested that the dipsogenic response to isoproterenol is mediated through angiotensin II. In the present study the angiotensin II-induced (200 micrograms/kg, s.c.) dipsogenic response was abolished by naloxone pretreatment. However, pretreatment with an equimolar dose of naloxone methobromide, an opiate antagonist which does not cross the blood-brain barrier, was ineffective in altering the dipsogenic response produced by peripheral administration of either angiotensin II or isoproterenol. Collectively, the data suggest that opiates do not alter peripheral beta-adrenergic responses and that the blocking effects of naloxone on the isoproterenol-induced drinking response is mediated centrally and may be due to blocking angiotensin II dipsogenesis.
Katovich
M J
MJ
University of Florida, Gainesville.
Barney
C C
CC
Larsen
E
E
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000187:drug effects*; D004326:Drinking / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects*; D007279:Injections, Subcutaneous; D007545:Isoproterenol / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D011292:Premedication; D051381:Rats; D011919:Rats, Inbred Strains
D000804:Angiotensin II; D009270:Naloxone; D007545:Isoproterenol